1. Field of Invention
The present invention relates to a low-maintenance high-pressure viscometer which includes a pressure vessel containing a movable piston assembly which separates a test sample from a pressurization fluid. The piston assembly also allows for the transfer of torque into the test sample by means of a rotatable shaft extending through the piston, while maintaining the required seal integrity of all chambers under conditions of temperature and pressure conducive to high-pressure, high-temperature viscosity tests.
2. Description of Prior Art
In connection with the drilling of oil and gas wells, drilling fluid is commonly used to drive the drill bit and bring sand and stone cuttings back to ground surface. The viscosity property of drilling fluid is critical in the drilling process. A drilling fluid with excessive viscosity would make it difficult to pump it down to the bore hole, while a drilling fluid with insufficient viscosity would make it difficult to carry sand and stone cuttings back to ground surface. The viscosity property of a drilling fluid varies significantly with the change of temperature and pressure. Thus a viscometer capable of closely simulating down-hole conditions with low maintenance is of great interest. Down-hole conditions are typically from room temperature and pressure up to 40,000 psi and 600° F.
U.S. Pat. No. 7,287,416—LOW MAINTENANCE HIGH PRESSURE VISCOMETER teaches a viscometer which meets these criteria to a great degree, but allows the test sample to come into direct contact with a magnet. This would prevent the accurate measurement of many high-density drilling muds because hematite is a common component of most high-density drilling muds. Hematite materials in high-density muds would be attracted to the magnet, thus causing inaccurate measurement. Prior art U.S. Pat. No. 7,287,415 also does not allow the testing of corrosive samples that would react with the magnet.
It is an object of this invention to provide a high-pressure viscometer wherein viscosity is determined under conditions closely simulating down-hole conditions.
It is another object of this invention to provide a high-pressure viscometer that provides a plurality of pressurizable test chambers.
It is another object of this invention to provide a high-pressure viscometer that provides a testing environment in which tested sample is kept entirely isolated and uncontaminated.
It is another object of this invention to provide a viscometer that requires substantially less maintenance work yet meets industry standards of accuracy, repeatability, durability, and ease of cleaning.